US4940057A - Apparatus for measuring brain function using nuclear magnetic resonance - Google Patents

Apparatus for measuring brain function using nuclear magnetic resonance Download PDF

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Publication number
US4940057A
US4940057A US07/073,718 US7371887A US4940057A US 4940057 A US4940057 A US 4940057A US 7371887 A US7371887 A US 7371887A US 4940057 A US4940057 A US 4940057A
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magnetic field
brain
head
coils
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Hirotake Kamei
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National Institute of Advanced Industrial Science and Technology AIST
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Agency of Industrial Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
    • G01R33/34046—Volume type coils, e.g. bird-cage coils; Quadrature bird-cage coils; Circularly polarised coils
    • G01R33/34061—Helmholtz coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/34—Constructional details, e.g. resonators, specially adapted to MR
    • G01R33/341—Constructional details, e.g. resonators, specially adapted to MR comprising surface coils
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
    • G01R33/48—NMR imaging systems
    • G01R33/4806—Functional imaging of brain activation

Definitions

  • This invention relates to a brain function measuring apparatus which uses nuclear magnetic resonance to discriminate and measure differences between the functions of the left and right hemispheres of a brain in vivo, the state of the functioning and the active portion locations.
  • NMR nuclear magnetic resonance
  • the resonance signals In the determination of brain functions using the above type of NMR technique, when the resonance signals from protons in water or loosely-bound fats at the site of the activity are observed, the resonance signals undergo minute changes that are in accordance with the blood flow amount, the blood flow velocity and the residual blood amount.
  • the obtained resonance signals are not only from protons in the blood flow, but are instead from protons in all the tissues, and the intensity fluctuation in resonance signals coming from the blood flow accompanying brain activity will account for no more than about 0.01 to 0.1 ppm of the resonance signals from the whole of the tissues.
  • an object of the present invention is to provide a brain function measuring apparatus which utilizes NMR for the high-resolution measurement of just the changes in the resonance signal produced by in vivo brain activity, and thereby enables the active part and state of activity of the brain to be recognized accurately.
  • the brain function measuring apparatus is comprised of magnetic excitation coils and resonance detection means provided with two coils positioned symmetrically to the left and right relative to the median line of the head of the subject.
  • a resonance signal detector comprises balanced circuits of a plurality of coil pairs which operate under a magnetic field gradient.
  • the differential component of the resonance signal output produced in each pair of coils is manifested as output from the detection circuit.
  • the active part and state of activity of the brain can then be recognized by analyzing the phase and amplitude of this differential signal.
  • processing such as Fourier transform processing, a tomographic image of the active portion of the brain can be displayed.
  • FIG. 1 is an abbreviated explanatory drawing of one embodiment of the brain function measuring apparatus of the present invention
  • FIG. 2 is an abbreviated explanatory drawing of another embodiment
  • FIGS. 3(a) to 3(d) show brain activity waveforms resulting from experiments using the apparatus of the present invention.
  • FIG. 4 is an abbreviated block diagram of another embodiment of the present invention.
  • a detection means 1 is comprised of NMR signal detection coils 2 and 3 which are arranged symmetrically in opposition to each other on each side of the median line L of a subject's head S to constitute a differential coil.
  • the numeral 4 denotes rotational magnetic field exciting coils disposed in the vicinity of the subject portion, and B 0 is the magnetic flux density of a static magnetic field.
  • the detection coils 2 and 3 are connected differentially so that the NMR signal arising in one coil has a phase that is the opposite of the NMR signal arising in the other coil.
  • the free induction signals obtained by the coils 2 and 3 cancel each other out, and as a result little signal appears at the output terminal (OUT).
  • Brain activity such as cerebration or an external stimulus causes a difference in the blood flow velocity, blood flow amount and residual blood amount between the right and left hemispheres in the subject's head S. Therefore, by using the coils 2 and 3 of the detection means 1 to detect the changes in blood states, a difference will be produced between the free induction decay signals detected by one of the coils and that detected by the other. As a result, the free induction signal differential component is manifested as an output signal.
  • the amplitude of the output signal indicates the hemisphere function differential for discriminating the brain activity, while the phase indicates the dominant hemisphere that produced the stronger of the free induction decay signals obtained from the two sides.
  • the exciting rotational magnetic field for producing the free induction signal can be applied by the exciting coil 4, or it may instead be applied by the coils 2 and 3.
  • FIG. 2 shows the working principle of an embodiment which uses a balanced detector in place of the differential type free induction decay signal detector coil of the foregoing embodiment.
  • the resonance signal detection means 1 is comprised of coils 5 and 6 and coils 7 and 8 arranged symmetrically on each side of the subject's head S with respect to the median line L of the head, and balanced detectors 9 and 10 to which are input the respective signals induced in the said coils 5 and 6 and coils 7 and 8.
  • the balanced detectors 9 and 10 are comprised of variable capacitors CV1 and CV2, capacitors C1 to C3, and coils L1 to L4.
  • Coils L2 and L3 are wound in mutually opposite directions. If the balanced detectors 9 and 10 are set to be in equilibrium when the brain is at rest, signals induced between the two pairs of coils 5, 6 and 7, 8 are cancelled out and no output appears at the output terminals of the balanced detectors 9 and 10. When the resonance signals produced as a result of brain activity shows a difference between the right and left hemispheres of the brain, the difference signal produces an output at the output terminals of the balanced detectors 9 and 10. The amplitude thereof enables right-left hemisphere activity to be differentiated; and, from the phase thereof, it can be ascertained which hemisphere was more active.
  • the exciting rotational magnetic field for producing the free induction signal can be applied by the coils 5, 6 and coils 7, 8, or by the exciting coil 4.
  • a linear magnetic field gradient is applied perpendicularly to the median line L and the information relating to the position is obtained as changes in the resonance frequency, thereby enabling the position of the active portion to be known.
  • the resolution of the position discrimination can be improved by increasing the number of coil-pairs.
  • FIGS. 3(a) to 3(d) show examples of actual measurements conducted using the apparatus of the above embodiment.
  • FIG. 3(a) is the waveform of a resonance signal obtained from the left hemisphere when the subject was given a mathematically oriented task to do
  • FIG. 3(b) is the waveform of a signal from the left hemisphere when the subject was listening to a Latin rhythm while the waveforms of FIGS. 3(c) to 3(d) were obtained from the right hemisphere when the subject was listening to music.
  • the aforementioned music was fusion music; and in the case of FIG. 3(d) it was classical music.
  • FIG. 4 shows another embodiment employing the type of balanced detector shown in FIG. 2.
  • parts that are the equivalent of the parts in the embodiment shown in FIG. 2 have been numbered the same, and further explanation thereof is therefore omitted.
  • the numerals 5', 6', 7' and 8' are coils; 9' and 10' are balanced detectors; 11, 11' and 12, 12' are high-frequency amplifiers/phase sensitive detectors; 13, 13' and 14, 14' are low-frequency amplifiers; 15, 15' and 16, 16' are A/D converters; 17 is a processing section; 18 is a display-recorder section; 19 is a high-frequency pulse generator; and 20 to 23 are magnetic gradient generating coils.
  • the high-frequency pulse generator 19 sends high-frequency current through the coil 4 in pulses of a fixed duration, tilting the magnetization vectors, which had been oriented in the direction of the static magnetic field, and producing magnetization vectors perpendicular to the static magnetic field, i.e., horizontal magnetization vectors. After the application of high-frequency pulses is stopped, the energy level of the horizontal magnetization vectors undergoes a reversion from the excited state to the ground state, which induces a high-frequency current in the detection coils 5 to 8 and 5' to 8'. This is the resonance signal.
  • the NMR frequency ( ⁇ 0 ) is shown by ⁇ B 0 and is proportional to the magnetic flux density B 0 of the static magnetic field.
  • ⁇ is a constant peculiar to the type of nucleus. If a magnetic field gradient is now applied symmetrically with respect to the median line L, the resonance frequencies at positions that are symmetrical with respect to the median line L (coil 6 with respect to coil 5, and so forth) will become mutually equal. If the magnitude of the magnetic field gradient is known beforehand, from the resonance frequency, the position of the active portion of the brain from the median line L can be found.
  • the high-frequency current induced in coils 7 and 8 are applied to the balanced detector 10 as signals of opposite phase. If the phase relationship in the balanced detectors 9, 10 and 9', 10' is known before hand, it can be known from the phase of a detected signal whether the active portion is in the left cerebral hemisphere or the right hemisphere. The location of the active portion can be established three-dimensionally, i.e. from the position of the detection coil, the phase of the detected signal, and the frequency. When the signal intensity is sufficiently high, the low-frequency amplifiers 13, 14 and 13', 14' can be dispensed with.
  • a tuning condenser may be added to each detection coil, and after high-frequency amplification the signal may be conducted to the balanced detectors 9, 10 and 9', 10'. Or, the signal may be conducted to the balanced detectors 9, 10 and 9', 10' after phase shift detection.
  • the coils will only output a resonance signal produced by brain activity. Therefore, the minute resonance signals do not get buried by resonance signals that are not from the intended object of detection, making it possible to perform the signal detection with a high resolution and high S/N ratio, thereby enabling the active portion of the brain, and the active state, to be recognized.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
US07/073,718 1986-07-15 1987-07-15 Apparatus for measuring brain function using nuclear magnetic resonance Expired - Fee Related US4940057A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP61-166115 1986-07-15
JP61166115A JPS6321049A (ja) 1986-07-15 1986-07-15 核磁気共鳴現象を用いた脳機能計測装置

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5303705A (en) * 1992-05-01 1994-04-19 Nenov Valeriy I Evoked 23NA MR imaging of sodium currents in the brain
US5325854A (en) * 1990-11-12 1994-07-05 Instrumentarium Corporation Magnetic resonance imaging
US5427100A (en) * 1992-02-07 1995-06-27 Hitachi, Ltd. Method for determining median line
US5842980A (en) * 1993-12-28 1998-12-01 Hitachi Medical Corporation Magnetic resonance inspecting method and apparatus
CN103126671A (zh) * 2013-03-27 2013-06-05 中国人民解放军第三军医大学 一种非接触的磁感应式脑出血检测系统
CN108209876A (zh) * 2018-02-09 2018-06-29 武汉技兴科技有限公司 人体头部三维定位及头皮状态建模的方法和装置
US11561270B2 (en) * 2019-08-30 2023-01-24 Electronics And Telecommunications Research Institute Apparatus and method for nano magnetic particle imaging

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4793356A (en) * 1985-08-14 1988-12-27 Picker International, Inc. Surface coil system for magnetic resonance imaging

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4528985A (en) * 1981-12-21 1985-07-16 Albert Macovski Blood vessel imaging system using nuclear magnetic resonance
US4565968A (en) * 1983-02-16 1986-01-21 Albert Macovski Blood vessel projection imaging system using nuclear magnetic resonance
JPS60376A (ja) * 1983-06-15 1985-01-05 Yokogawa Medical Syst Ltd 核磁気共鳴イメ−ジング装置におけるｒｆコイル装置
DE3347597A1 (de) * 1983-12-30 1985-07-18 Philips Patentverwaltung Gmbh, 2000 Hamburg Hochfrequenz-spulenanordnung zum erzeugen und/oder empfangen von wechselmagnetfeldern
US4724389A (en) * 1985-05-08 1988-02-09 Medical College Of Wisconsin, Inc. Loop-gap resonator for localized NMR imaging

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4793356A (en) * 1985-08-14 1988-12-27 Picker International, Inc. Surface coil system for magnetic resonance imaging

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5325854A (en) * 1990-11-12 1994-07-05 Instrumentarium Corporation Magnetic resonance imaging
US5427100A (en) * 1992-02-07 1995-06-27 Hitachi, Ltd. Method for determining median line
US5303705A (en) * 1992-05-01 1994-04-19 Nenov Valeriy I Evoked 23NA MR imaging of sodium currents in the brain
US5842980A (en) * 1993-12-28 1998-12-01 Hitachi Medical Corporation Magnetic resonance inspecting method and apparatus
CN103126671A (zh) * 2013-03-27 2013-06-05 中国人民解放军第三军医大学 一种非接触的磁感应式脑出血检测系统
CN103126671B (zh) * 2013-03-27 2015-08-19 中国人民解放军第三军医大学 一种非接触的磁感应式脑出血检测系统
CN108209876A (zh) * 2018-02-09 2018-06-29 武汉技兴科技有限公司 人体头部三维定位及头皮状态建模的方法和装置
CN108209876B (zh) * 2018-02-09 2023-04-28 武汉技兴科技有限公司 人体头部三维定位及头皮状态建模的方法和装置
US11561270B2 (en) * 2019-08-30 2023-01-24 Electronics And Telecommunications Research Institute Apparatus and method for nano magnetic particle imaging

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JPS6321049A (ja) 1988-01-28

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